Thanks guys. I took out the spare tire assembly and hacked off the mufflers (exhaust is being replaced) to get to the tank. It was wet along the support bar on the passenger side but I didn't find where it was coming from. I ordered a new tank to be safe and willl replace the gaskets. Unfortunately, this was not the original tank, so no tank sticker. There was a thick, greasy film on the tire assembly, especially on the top side of the upper part (facing the gas tank). I'm having a hard time cleaning it off and have tried dish soap in hot water, WD-40 and engine degreaser. I got some on my hands and have washed with soap, dish soap, shampoo, vinegar, lemon juice and everything else the internet recommends. What is this?!?! I assume it's buildup from leaking gasoline mixed with possibly dirt. Any suggestions?? Removing this is key to it being garaged since the smell permeates through my whole house just by being in the garage.
I will be pulling the seats out for new padding and covers as well as replacing the carpet and will follow your advice on searching for rodents while I'm at it. I did find some nuts behind the seats.